Apparatus for mixing fluids in a well



June 1964 J. P. CHISHOLM ETAL 3,139,142

APPARATUS FOR MIXING mums IN A WELL Filed Oct. 3, 1961 2 Sheets-Sheet 150 49 Y K K IN V EN TORS. James R 6/2 Ashe/m Joseph R Moran IQGENT June1964 J. P. CHISHOLM ETAL 3,139,142

APPARATUS FOR MIXING mums IN A WELL 2 Sheets-Sheet 2 Filed Oct. 3, 1961IN VEN TORS. James R C/wls/zo/m Joseph P. Mara/1 BY C. M 3

I96 E N T United States Patent 3,139,142 APPARATUS FOR MIXING FLUIDS INA WELL James P. Chisholm and Joseph P. Moran, both of Tulsa,

(Eda, assignors to The Dow Chemical Company, Midland, Mich, acorporation of Delaware Filed Oct. 3, 1961, Ser. No. 142,634 4 Claims.(Cl. 156-224) This invention relates to an apparatus for moxing fluidsand more particularly is concerned with a tool for mixing two fluidsdownhole in a well bore.

Many times in well treating operations it is desirable to mix fluidsdownhole in a well in order to take advantage of some feature of themixing such as an exothermic or endothermic reaction, formation of a gelor precipitate, etc. Because of the length of time involved in placingsuch mixtures in a well after blending them on the surface, it is oftenimpossible to get the mixture into the well at a predetermined place ata given time. Also, fluids which are safe to handle alone may producemixtures which are dangerous to handle.

Heretofore, a preferred method of mixing fluids downhole in a well borehas been to pump one fluid down the well tubing and a secondsimultaneously down the annulus between the well casing and the tubingallowing these to come together at the end of the string of tubing.However, results obtained by this technique are not entirelysatisfactory for many times only a small amount of intermingling of thefluids is found. This is especial- 1y true if the fluids haveappreciable differences in density. The more dense fluid quickly settlesand very often there is very litle mixing of the two fluids.

The tool of the present invention eliminates these problems and offersas its principal advantage a very satisfactory means for intimatelymixing fluids downhole in a well.

It is another object of the present invention to provide a downholemixing tool whereby materials that are safe to handle by themselves butwhich provide dangerous to handle mixtures can readily and safely bemixed in a well. It is a further object of the present invention toprovide a tool whereby fluids can be mixed at a predetermined place in awell bore and at a predetermined time.

The foregoing and other objects and advantages will be apparent fromreading the detailed description presented hereinafter in accordancewith the accompanying drawings.

In the drawings:

FIGURE 1 is an elevation in section of a Well bore hole with thedownhole mixing tool inserted therein.

FIGURE 2 is an enlarged section of the well bore hole of FIGURE 1 in thearea of the tool.

FIGURE 3 is a sectional view of one embodiment of the tool of thepresent invention.

FIGURE 4 is a transverse section of the tool taken alone line 4-4 ofFIGURE 3.

FIGURE 5 is a transverse section of the tool taken along line 55 ofFIGURE 3.

FIGURE 6 is an exploded view of a conical check valve assembly used inthe tool shown in FIGURE 3.

FIGURE 7 is an enlarged orthographic vertical section of a ball checkvalve assembly used in the tool shown in FIGURE 3.

In general the downhole mixing tool of the present invention comprises atubular member which is attachable to the bottom of a well tubing andwhich can be slidably inserted into a second tubing of larger diameterpositioned in a well bore. The bottom of the tool is attachable into asealing means by which the annular space between the two strings oftubing is sealed off. The tubular member has a through passage thecenter axis of which coincides with the center axis of the tubing whenit is attached thereto. The tubular member has check valves mounted inits internal through passage which valves define the top and bottom of amixing chamber and are positioned so that a fluid can be moved downthrough the well tubing into the mixing chamber and out of the bottom ofthis chamber. In the area between the two valves which define the topand bottom of the mixing chamber, there are a plurality of check valvesmounted in the wall of the tubular member through which a second fluidcan be moved from the annular spacing between the well tubing and secondlarger diameter tubing into the mixing chamber.

In actual practice ordinarily the mixing tool is attached to the bottomof a string of small bore well tubing, com monly known in the well artas a macaroni string or macaroni tubing which in turn is positionedinside a larger diameter regular well tubing. These tubings in turn areplaced in a cased or uncased well bore. Alternatively, the mixing toolcan be attached to the bottom of the regular well tubing and the Wellcasing itself can serve as the second larger diameter tubing.

One embodiment of the downhole mixing tool of the present invention asshown in the figures comprises a two-membered hollow tubular unit 10.

The top member 11 of the unit 10 has an externally threaded collar 12 atits upper end whereby the tool is coupled to the bottom end of amacaroni tubing string (not shown). The member 11 at about its midpointhas a shouldered ring 13 projecting outwardly from the face 14 of theinternal through passage 15. A ring-like valve seat 16 mating with thering 13 is attached thereto by press fitting, welding or otherconventional means. The valve seat 16 accepts the conical head member 17of a check valve assembly 18. The valve head 17 has a cylindrical shaft19 extending outwardly from the base 20 of the valve head 17. This shaft19 has a diameter less than that of the base 20. A coil spring 21 isfitted over the end of the shaft 19. The other end of the spring 21 isfitted into a recessed shouldered opening 22 in the center of the top ofa threaded spring retainer 23 which has been screwed into mating threads24 cut into the face 14 of the lower end of passage 15 The springretainer 23 is held secure by an open-center threaded retaining lockmember 25, also screwed into the threaded portion of passage 15 until itfits tightly against the bottom of the retainer 23. Below the threads24, the passage 15 of member 11 is widened and contains internal threads26. The lower tubular member 27 has an externally threaded collar 28 atits top, the threads of which mate with threads 25 whereby the lowermember 27 is joined tightly to the upper member 11. This member 27 hasan internal passage 29 containing a shouldered ring 30 below itsmidpoint to which is aflixed a valve seat 31 the same as described forthe top member 11. A second relief valve 18 having conical valve head17, shaft 19, coil spring 21, spring retainer 23 and retainer lock nut25 in fitted into the bottom portion of this member 27, the threadedmembers being screwed into mating threads 32 in the lower portion of thepassage 29'. The section of passage 29 above the conical relief valve isthe mixing chamber of the tool. Above the lower internal check valve 18and valve seat 31 and below the threaded collar 28 a number of ball-typecheck valves 33 are placed in the sidewall 34 of member 27. These valves33, as shown in the depicted embodiment of FIGURE 7 can be conventionalZerk type grease fittings, which are comprised of an externally threadedspring housing and ball seat 35, spring 36 and ball 37. Below thethreads 32, the passage 29 is widened and contains internal threads 38bywhich the tool is fastened to an externally threaded collar of aconventional seating cup 39.

"By changing the position of the spring retainer 23 and retainer locknut 25 along the threaded portion 24 in the upper member 11 or along thethreads 32 in the bottom member 27 of the tool the tension can bechanged on the springs 21 thereby affording a means of varying thepressure required to open the relief valve 18 in each of the two members11 and 27 of the tool 10.

Also, if desired, a number of holes can be placed in the spring retainer23 to facilitating fluid flow down through the lower part of passagesand 29 although these are not essential to the performance of the tool.

Flat surfaces can be formed into opposite sides of the outside wall ofeach of the members 11 and 27 as well as on the seating cup 39 for easyattaching of wrenches thereto when loosening or tightening the sections.

One embodiment of a well assembly into which th tool of the instantinvention had been incorporated is shown in FIGURE 1. In this assembly abell-shaped perforated member 41 was fastened as by welding onto thebottom of a well tubing 42. At a predetermined distance above member 41a thick Walled nipple 43, i.e., a conventional seating nipple, wasplaced in the tubing 42. The tubing 42 then was positioned into a casedwell bore in an earth formation and sand poured into the hole to fillthe annular space between the hole and the tubing 42 to a point a shortdistance above the top of the bell shaped end member 41. The top member11 of the instant tool was coupled to the bottom of a second string ofsmaller-diametered tubing 44, i.e. a macaroni string which fits insidethe regular well tubing 42 leaving an annulaus 45 between the two setsof tubing. The bottom member 27 of tool 10 in turn is attached to themember 11 and a seating cup 39 attached to the bottom of member 27. -Theseating cup can be of conventional 1 design, e.g. having a series ofTeflon packing rings 46 around its periphery which provide a liquidrestraining seal when in place in the seating nipple 43. Above the wellthe macaroni string 44 is packed off from the tubing 42 by aconventional stuffing box 47. A feed line 48 fitted with a check valveto prevent backward flow is attached to the tubing 42 communicating withthe annular passage 4.5. feed lines with a check valve in each line anda common control valve 50 is attached to the top of the macaroni string44.

In the embodiment shown in FIGURE 1, the bell shaped member 41 is shownresting on the bottom of a well. It is to be understood, however, thatby use of packers and sealers, a well bore can be sealed off at anypredetermined point and the tool then be utilized for treatment at orabove the position.

The materials of construction to be used for the tool and the welltubing can be selected from any of a variety of structural materialsthat are resistant to attack by the chemicals being pumped and have therequisite strength for operation at the pressures involved. Stainlesssteels and other ferrous, chrome or nickel based alloys asconventionally used for well tubing and well assemblies have been foundto be suitable.

In operation, a fluid is introduced under pressure into the macaroni,tubing 44 and passes through the coni cal relief valve 18 in the uppertool'member 11 into the mixing chamber of the tool. Simultaneously asecond fluid is pumped down through the annulus 45 between the macaronitubing 44 and the well tubing 42 and through the ball valves 33 alsointo the mixing chamber whereupon ready mixing of the liquids results.Once in this chamber the mixture cannot flow back out through theone-way ball valves in the chamber wall 34 or up through the one-wayrelief valve 18 in the through passage 15 of upper tool member 11. Theapplied fluid pressure forces open the relief valve 18 in the bottom ofA feed assembly 49 having two chamber down through the interior of thetubular seating cup 39 on through the well tubing 42 below the mixingtool 10 and out into the formation through the perforated bell shapedmember 41 at the bottom of the tubing 42.

The utility of the tool of this invention is further shown by thefollowing examples but is not meant to be limited thereto.

' Example 1 A 4.5 inch diameter well 42 feet deep was drilled into asoft limestone formation. About 40.5 feet of nominal 2 inch (I.D.) steeltubing (2% inch O.D.) was run into the open hole. For this test the 2inch I.D. tubing served both as well casing'and well tubing. Welded tothe bottom of this tubing was a 15 inch long bell-shaped member havingan outside diameter of about 4 inches at the bottom and containing about24% inch diameter holes around its periphery.

A 6 inch long thick-walled seating nipple, inside diameter about 1%inch, had been placed in the well tubing string at a point which wasabout 20 feet from the ground surface.

After positioning the tubing in the well, about 10 pounds of 4060 meshsand (US. Standard Sieve Series) was poured into the hole to fill theannular space between the open hole and the tubing to a point about 0.5foot above the top of the bell-shaped member. The remaining annularspace from the top of the sand to the surface was filled with cement.

The well was hydraulically fractured following conventional proceduresusing about 200 gallons of a semirefined oil, viscosity about 200 cps.,as is widely used for fracturing wells. The oil contained about 700pounds of 40-60 mesh sand propping agent. For the fracturing operation,the slurry of sand and fracturing fluid was pumped into the formation ata pressure of about 350 pounds per square inch.

About 19 feet of 1 inch diameter 304 stainless steel macaroni tubing,having the tool of the invention and a seating cup affixed to the bottomof the string was run into the well, until the seating cup engaged theseating nipple in the 2 inch tubing string. The top of the macaronistring was packed off from the 2 inch tubing with a 2 x 1 inch pumpstuffing box. A single feed line was attached to the 2 inch tubing and adual feed system was joined to the top of the macaroni string.

Four gallons of 2-nitropropane (density8.34 lb./ gal.) were pumped downthe annular space between the macaroni string and the 2 inch tubing, andduring the same time period, 6 gallons red fuming nitric acid containing14 percent N0 (density-l3 lb./ gal.) were pumped down the macaronistring. The 2-nitropropane passed down the annulus, through theball-type check valves in the side of the tool and intothe mixingchamber; The fuming nitric acid passed down the macaroni string, throughthe conical pressure relief valve above the mixing chamher and into thechamber. The two fluids after mixing in the chamber were forced outthrough the conical relief valve in the bottom of the mixing chamber,down the 2 inch pipe and through the bell-shaped member out into theformation.

The two fluid components, fuming nitric acid and 2- nitropropane, bythemselves, are not explosively dangerous. However, mixtures of thesefluids can be readily detonated and ltherefore are somewhat dangerous tohandle.

After the fluids had been mixed, 1.2 gallons additional 2-nitropropanewere pumped down the annulus and at the same time 1.8 gallons2-nitropropane were pumped down the macaroni string to flush out thefuming nitric acid. The control valve at the top of the macaroni stringwas then switched from the fuming nitric acid feed line to the otherline containing igniter. About 4 gallon percent phosphoric acid waspumped through the igniter line followed in order by 1 gallonZ-nitropropane and by gallons of a mixture composed of 7.5 gallonsfurfural alcohol and 2.5 gallons aniline, the latter compound being theigniter. The phosphoric acid and Z-nitropropane were used simply asadditional flush materials to help remove the fuming nitric acid fromthe macaroni string. The igniter passed on down the well straightthrough the check valves in the tool and was forced out into theformation where it contacted the mixture of 2-nitropr0pane and nitricacid detonating the same. Proof of detonation was obtained by seismicinstruments positioned near the well. Since detonation of this explosivemixture by this igniter does not occur unless the components,Z-nitropropane and fuming nitric acid, have been thoroughly mixed inproper proportions, this test was evidence that good mixing had beenobtained by the tool of this invention.

Example 2 The operability of the tool also was shown in surface testsusing the same assembly as described for Example 1 where about 3 gallonsof carbon tetrachloride (density about 1.6 grams per cubic centimeter)containing about 0.1 percent by weight of oil red dye were pumped down a1 inch diameter macaroni pipe and into the mixing tool. At the sametime, about 2 gallons of kerosene (density about 0.8 gram per cubiccentimeter) were pumped down the annulus between the macaroni pipe and a2 inch tubing and into the mixing chamber through the ball check valvesin the sidewall of the tool. The fluid coming through the valve at thebottom of the mixing tool was sampled during the run. All samples asdetermined by direct visual observation appeared to be of homogeneoustexture and color with no stratification of the two difierent densityfluids.

Various modifications can be made in the present invention withoutdeparting from the spirit or scope thereof for it is understood that welimit ourselves only as defined in the appended claims.

We claim:

1. A downhole mixing tool adapted to be connected to the lower end of asmall bore well tubing and slidably inserted into a second largerdiameter well tubing in a well bore which comprises; a tubular memberattachable to the bottom of a small bore well tubing so that the centeraxis of the through passage of said tubular member coincides with thecenter axis of said small bore well tubing when attached thereto, asecond larger diameter well tubing the bottom of said tubular memberbeing attachable through a sealing means to said second larger diametersurrounding well tubing whereby the annular space between said smallbore well tubing and said second larger diameter well tubing is sealedoff, said tubular member having two check valves in spaced apartrelationship in said through passage, said valves defining the top andbottom of a mixing chamber, the upper of said check valves providing forthe introduction of a first fluid from said small bore well tubing intosaid mixing chamber, a plurality of check valves mounted in the sidewall of said tubular member above said sealing means and between thesaid tube valves defining the top and bottom of said mixing chamber insaid through passage, said plurality of check valves in the side wall ofsaid tubular member providing for the introduction of a second fluidfrom the annular spacing between said small bore Well tubing and saidsecond larger diametered well tubing into said mixing chamber an thelower of said check valves defining the bottom of said mixing chamber insaid through passage of said tubular member providing for the removal ofthe resulting mixture of said first and second fiuids through the bottomof said mixing chamber.

2. The downhole mixing tool as defined in claim 1 wherein the two checkvalves defining the top and bottom of the mixing chamber of said tubularmember are adjustable check valves, said valves being adjusted in thethrough passage so as to be opened by fluid force of a givenpredetermined pressure.

3. A downhole mixing tool adapted to be connected to the lower end of amacaroni well tubing and slidably inserted into the tubing in a wellbore which comprises; a two-member, hollow tubular unit, the top memberof said unit having a threaded collar at its upper end whereby saidmember can be coupled to the end of said macaroni tubing, said memberhaving a valve seat in its through passage, said valve seataccommodating a first check valve, said check valve providing for theintroduction of a first fluid under pressure from said macaroni tubinginto said tubular member, said top tubular member having a couplingmeans at its lower end, said coupling means mating with a secondcoupling means in the top of the lower tubular member of said tool, saidlower member having a plurality of check valves in its side wall belowsaid coupling means, said check valves in the side wall of said lowermember providing for the introduction into said lower member of a secondfluid from the annulus between said macaroni well tubing and the welltubing, a valve seat in the through passage of said lower tubular memberbelow said check valves in its side wall, said valve seat in said lowermember accommodating a check valve similar to said check valve in saidupper member, said check valve providing for the removal of theresulting mixture of said first and second fluids through the bottom ofsaid lower tubular member, a sealing means, and said lower member havinga coupling means at its lower end for fitting said member into saidsealing means, said sealing means providing a liquid restraining seal inthe annulus between said macaroni tubing and said well tubing.

4. The downhole mixing tool as defined in claim 3 wherein the checkvalves in the through passage are adjustable check valves, said checkvalves thereby affording through their means of adjustment control in apredetermined manner of the pressure required to open said valves.

Crawford Nov. 17, 1959 Wilder June 26, 1962

1. A DOWNHOLD MIXING TOOL ADAPTED TO BE CONNECTED TO THE LOWER END OF ASMALL BORE WELL TUBING AND SLIDABLY INSERTED INTO A SECOND LARGERDIAMETER WELL TUBING IN A WELL BORE WHICH COMPRISES; A TUBULAR MEMBERATTACHABLE TO THE BOTTOM OF A SMALL BORE WELL TUBING SO THAT THE CENTERAXIS OF THE THROUGH PASSAGE OF SAID TUBULAR MEMBER COINCIDES WITH THECENTER AXIS OF SAID SMALL BORE WELL TUBING WHEN ATTACHED THERETO, ASECOND LARGER DIAMETER WELL TUBING THE BOTTOM OF SAID TUBULAR MEMBERBEING ATTACHABLE THROUGH A SEALING MEANS TO SAID SECOND LARGER DIAMETERSURROUNDING WELL TUBING WHEREBY THE ANNULAR SPACE BETWEEN SAID SMALLBORE WELL TUBING AND SAID SECOND LARGER DIAMETER WELL TUBING IS SEALEDOFF, SAID TUBULAR MEMBER HAVING TWO CHECK VALVES IN SPACED APARTRELATIONSHIP IN SAID THROUGH PASSAGE, SAID VALVES DEFINING THE TOP ANDBOTTOM OF A MIXING CHAMBER, THE UPPER OF SAID CHECK VALVES PROVIDING FORTHE INTRODUCTION OF A FIRST FLUID FROM SAID SMALL BORE WELL TUBING INTOSAID MIXING CHAMBER, A PLURALITY OF CHECK VALVES MOUNTED IN THE SIDEWALL OF SAID TUBULAR MEMBER ABOVE SAID SEALING MEANS AND BETWEEN THESAID TUBE VALVES DEFINING THE TOP AND BOTTOM OF SAID MIXING CHAMBER INSAID THROUGH PASSAGE, SAID PLURALITY OF CHECK VALVES IN THE SIDE WALL OFSAID TUBULAR MEMBER PROVIDING FOR THE INTRODUCTION OF A SECOND FLUIDFROM THE ANNULAR SPACING BETWEEN SAID SMALL BORE WELL TUBING AND SAIDSECOND LARGER DIAMETERED WELL TUBING INTO SAID MIXING CHAMBER AN THELOWER OF SAID CHECK VALVES DEFINING THE BOTTOM OF SAID MIXING CHAMBE INSAID THROUGH PASSAGE OF SAID TUBULAR MEMBER PROVIDING FOR THE REMOVAL OFTHE RESULTING MIXTURE OF SAID FIRST AND SECOND FLUIDS THROUGH THE BOTTOMOF SAID MIXING CHAMBER.